Rechargeable battery and battery module

ABSTRACT

A rechargeable battery includes an electrode assembly having positive and negative electrodes and a separator interposed between the positive and negative electrodes, a case for receiving the electrode assembly, and a plurality of projections formed on an outer surface of the case.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2005-0024500 filed on Mar. 24, 2005, and10-2005-0061122 filed on Jul. 7, 2005, both applications filed in theKorean Intellectual Property Office, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rechargeable battery, and moreparticularly, to a rechargeable battery that is improved in its heatdissipation efficiency and a battery module having such rechargeablebatteries.

2. Description of the Related Art

Unlike a primary battery, a rechargeable battery may be recharged. Lowcapacity batteries are used for various portable electronic devices suchas phones, laptop computers, and camcorders. High capacity batteries areused as the power source for driving motors, such as those for hybridelectric vehicles (HEV).

Depending on their external shape, rechargeable batteries may beclassified into different types, for example, prismatic and cylindricalbatteries.

The high capacity rechargeable battery (hereinafter, referred as“battery module”) are composed of a plurality of rechargeable batteries(hereinafter, each referred as “unit battery”) so that it can be used todrive motors of machines requiring a high power source such as hybridelectric vehicles. The unit battery includes an electrode assemblyhaving positive and negative electrodes and a separator interposedbetween the positive and negative electrodes, a case for receiving theelectrode assembly, a cap assembly for sealing the case, and positiveand negative terminals extending from the cap assembly and electricallyconnected to the positive and negative electrodes, respectively.

Conductive lead terminals are attached to the respective positive andnegative electrodes to collect current and induce the collected currentto the positive and negative terminals.

If the unit batteries are prismatic type batteries, the unit batteriesare arranged such that the positive and negative terminals of one unitbattery alternate with the positive and negative terminals of anadjacent unit battery. The adjacent positive and negative terminals ofthe adjacent unit batteries are electrically interconnected byconductive members to form the battery module.

The unit battery generates heat during the charge/discharge operation.The heat is generally dissipated to an external side through the case.The heat dissipation property of the unit battery is a very importantfactor on which the performance of the battery module depends.

When the heat dissipation is not properly realized, an internaltemperature of the unit battery increases to deteriorate the performanceof the unit battery. Sometime, the increased internal temperature maycause an explosion of the unit battery.

Since the battery module is comprised of several to tens of unitbatteries connected in series or parallel, the reaction heat generatedfrom the unit batteries must be more efficiently dissipated.

That is, if heat dissipation of the unit batteries is not properlyrealized, the internal temperature of the battery module may increaseexcessively. Accordingly, both the battery module and the device poweredby the battery module may malfunction.

Particularly, when the battery module is used as the high capacityrechargeable battery for driving motors of the HEV, the heat dissipationproperty of the unit battery is of significant importance. That is,since the charge/discharge operation of the battery module is done witha large capacity of current, the internal temperature of the batterymodule increases excessively. This deteriorates the inherent performanceof the battery module.

In addition, internal pressure of the unit battery increases due tointernal chemical reaction of the unit battery. The increased internalpressure may deform a shape of the battery unit. This may causesdeterioration of the battery performance. For the prismatic batteryhaving a relatively high aspect ratio, such problems become more severe.

To solve the problems, a plurality of barriers are disposed between theunit batteries to provide channels between the unit batteries. Ascooling air passes through the channels, the heat generated from theunit batteries is dissipated. However, this structure cannot yetsufficiently dissipate the heat out of the battery module. Furthermore,the battery shape deformation problem caused by the internal chemicalreaction is not still solved.

SUMMARY OF THE INVENTION

The present invention provides a rechargeable battery having a case thatis improved to maximize the heat dissipation area and a battery modulehaving such rechargeable batteries.

According to one embodiment of the present invention, there is provideda rechargeable battery including an electrode assembly having positiveand negative electrodes and a separator interposed between the positiveand negative electrodes; a case for receiving the electrode assembly;and a plurality of projections formed on an outer surface of the case.

The projections may be random in terms of a size, shape and arrangementthereof.

Each of the projections may have a circular or rectangular section.

Alternatively, the projections may be uniformly arranged in apredetermined pattern.

Preferably, the projections are distributed throughout the outersurface.

The case may be prismatic or cylindrical.

The projections may be integrally formed with the case.

The projections are formed such that a relative area of the outersurface of the case is about 150 or more when it is assumed that an areaof a case having an even outer surface is 100.

Preferably the relative area may be in the range from 150 to 1000, morepreferably, the relative area may be in the range from 175 to 1000.

According to another aspect of the present invention, there is provideda battery module including a housing having an inlet for introducingcooling air and an outlet for exhausting the introduced cooling air; anda plurality of unit batteries disposed in the housing, each unit batteryhaving a case whose outer surface is provided with a plurality ofprojections.

The battery module may further include barriers interposed between theunit batteries such that gaps are defined between the barrier and theunit battery by the projections.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a perspective view of a rechargeable battery according to anexemplary embodiment of the present invention;

FIG. 2 is a schematic view of a battery module, to which therechargeable batteries of FIG. 1 are applied as unit batteries,according to an exemplary embodiment of the present invention;

FIG. 3 is a perspective view of a rechargeable battery according toanother exemplary embodiment of the present invention;

FIG. 4 is a schematic view of a battery module, to which therechargeable batteries of FIG. 3 are applied as unit batteries,according to another exemplary embodiment of the present invention;

FIG. 5 is a perspective view of a rechargeable battery according toanother exemplary embodiment of the present invention;

FIG. 6 is a schematic view of a battery module, to which therechargeable batteries of FIG. 5 is applied as unit batteries, accordingto another exemplary embodiment of the present invention;

FIG. 7 is a perspective view of a rechargeable battery according toanother exemplary embodiment of the present invention;

FIG. 8 is a perspective view of a rechargeable battery according toanother exemplary embodiment of the present invention;

FIG. 9 is a perspective view of a rechargeable battery according toanother exemplary embodiment of the present invention; and

FIGS. 10A through 10K are schematic sectional views of outer surfaces ofthe examples 1 through 11 that are different in a relative surface areafrom each other.

DETAILED DESCRIPTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be through and complete, and will fully conveythe concept of the invention to those skilled in the art.

FIG. 1 shows a rechargeable battery according to an exemplary embodimentof the present invention;

A rechargeable battery 20 of this embodiment is a prismatic rechargeablebattery including a rectangular hexahedral case 21, an electrodeassembly 22 received in the case 21, a cap plate 23 for sealing anopening of the case 21. The electrode assembly 22 includes positive andnegative electrodes 22 b and 22 c and a separator 22 a formed of aninsulation material and interposed between the positive and negativeelectrodes 22 b and 22 c. An outer surface of the case 21 is roughlyprocessed such that fine projections E can be formed on the outersurface.

The positive and negative electrodes 22 b and 22 c of the electrodeassembly 22 are electrically connected to positive and negativeterminals 25 and 27 mounted on the cap plate 23, respectively.

The cap plate 23 is formed in a shape corresponding to the opening ofthe case 21. The positive and negative terminals 25 and 27 are projectedto an external side through holes formed on the cap plate 23.

The cap plate 23 is provided with a thin portion 29 that will be brokenwhen inner pressure of the rechargeable battery 20 increases above apredetermined level to prevent the rechargeable battery 20 fromexploding.

The case 21 may be formed of a conductive material such as aluminum, analuminum alloy or steel plated with nickel. Alternatively, the case 21may be formed of an insulation material such as a polyethylene,polypropylene or polytetrafluorethylene.

As shown in a circled portion of FIG. 1, the outer surface of the case21 is roughly processed to have the fine projections E. Therefore, acontact area of the case 21 with external air increases.

In this embodiment, the projections are different in a size and a shape.The roughness of the outer surface of the case is not limited to apredetermined degree.

Alternatively, the projections E may be separately prepared and attachedon the outer surface of the case 21. In this case, the projections E areformed of a material identical to that of the case 21 or a materialhaving a thermal conductivity higher than that of the case 21.

As the projections E are formed on the surface of the case 21, thecontact area of the case 21 with cooling air, thereby more effectivelydissipating reaction heat generated from the electrode assembly.

FIG. 2 is a schematic view of a battery module, to which therechargeable battery of FIG. 1 is applied as a unit battery, accordingto an exemplary embodiment of the present invention.

Referring to FIG. 2, a battery module of this embodiment includes ahousing 11 defining an internal space S and having an inlet 13 andoutlet 15 for the cooling air. A blower fan 17 is installed near theinlet 13 in the housing.

The unit batteries 20 are installed in the space S of the housing 11. Asdescribed with reference to FIG. 1, each unit battery 20 has projectionsE formed on the outer surface thereof.

A barrier 30 is disposed between the adjacent unit batteries 20. Airpassages are formed through the barrier 30 to allow the cooling air toflow between the adjacent batteries. The barrier 30 also functions tosupport side surfaces of the unit batteries 20.

Furthermore, since the projections are formed on the outer surfaces ofthe case 21 of the unit batteries 20, gaps G are formed between thebarrier 30 and the case 21. Therefore, the cooling air introducedthrough the inlet 13 passes through the air passages 31 formed throughthe barrier 30 as well as through the gaps G, thereby dramaticallyincreasing the heat dissipation efficiency. The projections E formed onthe unit battery 20 are formed of a heat conductive material.

That is, the cooling air is introduced into the housing 11 through theinlet 13 by the operation of the blower fan 17 and passes through theair passages 31 formed through the barriers 30 between the unitbatteries 20 as well as through the gaps defined between the unitbatteries 20 and the barriers 30, in the course of which the cooling airabsorbs the reaction heat generated from the unit batteries 20. Thecooling air 30 is then exhausted through the outlet 15.

FIG. 3 shows a rechargeable battery according to another exemplaryembodiment of the present invention.

A rechargeable battery 20 of this embodiment is a prismatic rechargeablebattery including a rectangular hexahedral case 21, an electrodeassembly (not shown) received in the case 21, a cap plate 23 for sealingan opening of the case 21. The electrode assembly 22 includes positiveand negative electrodes 22 b and 22 c and a separator 22 a formed of aninsulation material and interposed between the positive and negativeelectrodes 22 b and 22 c. A plurality of fine projections P1 arearranged on an outer surface of the case 21.

That is, in order to increase a contact area of the outer surface of thecase 21 with external air, the fine projections P1 are arranged on theouter surface of the case 21 in a predetermined pattern. The fineprojections P1 are spaced apart from each other and formed in aquadrangular pyramid shape including a diamond pyramid shape. Theprojections P1 may be integrally formed with the case 21. Alternatively,the projections P1 are separately prepared and attached on the case 21.In this case, the projections P1 are formed of a material identical tothat of the case 21 or a material having a thermal conductivity higherthan that of the case 21.

FIG. 4 is a schematic view of a battery module, to which therechargeable batteries of FIG. 3 are applied as unit batteries,according to another exemplary embodiment of the present invention;

Likewise the embodiment of FIG. 3, gaps G are defined between a case 21of each unit battery and a barrier 30 by the projections P1 arranged onthe outer surface of the case 21 in the predetermined pattern, therebyimproving the cooling efficiency.

FIG. 5 shows a rechargeable battery according to another exemplaryembodiment of the present invention.

A rechargeable battery 20 of this embodiment is a prismatic rechargeablebattery including a rectangular hexahedral case 21, an electrodeassembly (not shown) received in the case 21, a cap plate 23 for sealingan opening of the case 21. The electrode assembly 22 includes positiveand negative electrodes 22 b and 22 c and a separator 22 a formed of aninsulation material and interposed between the positive and negativeelectrodes 22 b and 22 c. A plurality of fine projections P2 arearranged on an outer surface of the case 21.

That is, in order to increase a contact area of the outer surface of thecase 21 with external air, the fine projections P2 are arranged on theouter surface of the case 21 in a predetermined pattern. The fineprojections P2 are spaced apart from each other and formed in a circularcylinder shape. The projections P2 may be integrally formed with thecase 21. Alternatively, the projections P2 are separately prepared andattached on the case 21. In this case, the projections P2 are formed ofa material identical to that of the case 21 or a material having athermal conductivity higher than that of the case 21.

FIG. 6 is a schematic view of a battery module, to which therechargeable batteries of FIG. 5 are applied as unit batteries,according to another exemplary embodiment of the present invention;

Likewise the embodiments of FIGS. 3 and 5, gaps G are defined between acase 21 of each unit battery and a barrier 30 by the projections P2arranged on the outer surface of the case 21 in the predeterminedpattern, thereby improving the cooling efficiency.

FIG. 7 shows a rechargeable battery according to another exemplaryembodiment of the present invention;

A rechargeable battery 120 of this embodiment is a cylindricalrechargeable battery including a cylindrical case 121, an electrodeassembly (not shown) received in the case 121, a cap assembly 123 forsealing an opening of the case 121. The electrode assembly includespositive and negative electrodes and a separator formed of an insulationmaterial and interposed between the positive and negative electrodes. Anouter surface of the case 121 is roughly processed such that fineprojections E can be formed on the outer surface.

An outer terminal 125 is electrically connected to the positiveelectrode of the electrode assembly and projected outward from the capassembly 123.

The case 121 may be formed of a conductive material such as aluminum, analuminum alloy or steel plated with nickel.

As shown in a circled portion of FIG. 7, the outer surface of the case121 is roughly processed to have the fine projections E. Therefore, acontact area of the case 121 with external air increases.

In this embodiment, the projections are different in a size and a shape.The roughness of the outer surface of the case is not limited to apredetermined degree.

As the projections E are formed on the surface of the case 121, thecontact area of the case 121 with cooling air, thereby more effectivelydissipating reaction heat generated from the electrode assembly.

FIG. 8 shows a rechargeable battery according to another exemplaryembodiment of the present invention.

A rechargeable battery 120 of this embodiment has a cylindrical case121. A plurality of fine projections P1 are arranged on an outer surfaceof the case 121.

That is, in order to increase a contact area of the outer surface of thecase 121 with external air, the fine projections P1 are arranged on theouter surface of the case 121 in a predetermined pattern. The fineprojections P1 are spaced apart from each other and formed in aquadrangular pyramid shape including a diamond pyramid shape. Theprojections P1 may be integrally formed with the case 121.

FIG. 9 shows a rechargeable battery according to another exemplaryembodiment of the present invention.

A rechargeable battery 120 of this embodiment has a cylindrical case121. A plurality of fine projections P2 are arranged on an outer surfaceof the case 121.

That is, in order to increase a contact area of the outer surface of thecase 121 with external air, the fine projections P2 are arranged on theouter surface of the case 121 in a predetermined pattern. The fineprojections P2 are spaced apart from each other and formed in a circularcylinder shape.

EXPERIMENTAL EXAMPLES

Eleven rechargeable batteries (examples 1 through 11) were preparedaccording to the embodiment of FIG. 5. These rechargeable batteries(example 1 through 11) were compared with the prior art rechargeablebattery (comparative example 1) having an even outer surface.

In order to prepare a positive electrode of the rechargeable batteries,LiGoO₂ was used as a positive active material, PVDF was used as binder,Super-P was used as a conductive material, and NMP was used as solvent.The positive active material, binder and conductive material were mixedwith each other at a weight ratio of 94:3:3. Slurry was prepared bydissolving the mixture in the solvent. The slurry was coated on analuminum current collector and dried. Then, the positive electrode wasprepared by pressing the aluminum current collector.

In order to prepare a negative electrode, carbon was used as a negativeactive material, PVDF was used as binder, and NMP was used as solvent.The negative active material and the binder were mixed with each otherat a weight ratio of 94:6. Slurry was prepared by dissolving the mixturein the solvent. The slurry was coated on a copper current collector anddried. The negative electrode was prepared by pressing the coppercurrent collector.

Using the positive and negative electrodes, eleven prismaticrechargeable batteries each having a thickness of 46 mm, a width of 34mm and a length of 500 mm were manufactured. At this point, 1.0M LiPF₆EC/DMC/EMC(3/3/4) was used as electrolyte.

Projections P2 different in a length from each other were formed onouter surfaces of the prismatic rechargeable batteries, therebypreparing the examples 1 through 11. These examples were compared withcomparative example 1 that is the prior art rechargeable battery havingan even outer surface.

FIGS. 10A through 10K are schematic sectional views of outer surfaces ofthe examples 1 through 11, that are different in a relative surface areafrom each other.

A relative surface area (RS) means a relative value when a surface areaof the comparative example was 100.

The projections were formed on the examples 1 through 11 such that arelative surface area RS of the first example is 125 (see FIG. 10A), arelative surface area RS of the second example is 150 (see FIG. 10B), arelative surface area RS of the third example is 175 (see FIG. 10C), arelative surface area RS of the fourth example is 200 (see FIG. 10D), arelative surface area RS of the fifth example is 225 (see FIG. 10E), arelative surface RS of the sixth example is 250 (see FIG. 10F), arelative surface area RS of the seventh example is 275 (see FIG. 10G), arelative surface area RS of the eighth example is 300 (see FIG. 10H), arelative surface area RS of the ninth example is 400 (see FIG. 101), arelative surface area RS of the tenth example is 600 (see FIG. 10J) anda relative surface area RS of the eleventh example is 1000 (see FIG.10K).

The rechargeable batteries were charged and discharged with 0.2 C onetime and further charged and discharged with 0.5 C and 0.2 C,respectively, one time. The capacity means a depth of discharge of astandard process.

A series of experiments were performed for the examples 1 through 11 andthe comparative example.

That is, the examples and the comparative example 1 were tested by beingcharged and discharged 300 times with 1.0 C at the normal temperature.

The examples and the comparative example 1 were tested by being chargedand discharged 300 times with 1.0 C at a temperature of 60° C.

The examples and the comparative example 1 were tested by being chargedwith 4.2V and penetrated.

The examples and the comparative example 1 were tested by beingovercharged with 4.35V and penetrated.

The examples and the comparative example 1 were tested by beingovercharged with 1.0 C.

The experimental results are shown in the following Table 1. TABLE 1Service life Service life Over Relative at normal at high Chargedcharged surface temperature - temperature with 4.2 V with 4.35 VOvercharged area Battery 300 times (60° C.) - 300 and and with (RS)capacity [%] times[%] penetration penetration 1.0 C Comparative 100 90070 46 Fire Fire Fire Example 1 Example 1 125 900 71 53 Fire Fire FireExample 2 150 900 73 57 Not fire Fire Not fire Example 3 175 900 75 64Not fire Not fire Not fire Example 4 200 900 76 66 Not fire Not fire Notfire Example 5 225 900 77 68 Not fire Not fire Not fire Example 6 250900 79 71 Not fire Not fire Not fire Example 7 275 900 80 72 Not fireNot fire Not fire Example 8 300 900 81 73 Not fire Not fire Not fireExample 9 400 900 82 73 Not fire Not fire Not fire Example 10 600 900 8273 Not fire Not fire Not fire Example 11 1000 900 82 73 Not fire Notfire Not fire

As can be noted from the Table 1, the examples manufacture according tothe present invention is superior to the comparative example 1 in termsof the service life and safety.

It can be further noted than when the relative surface area is more than1.5 times (examples 2 through 11), preferably, 1.75 times that of thecomparative example 1, the safety the batteries can be more improved.That is, since the heat generated in the batteries of the examples 2through 11 can be more effectively dissipated, an accident such as firecaused when excessive impact is applied to the battery can be prevented.

When the relative surface area is more than 1000, since the overallvolume of the battery excessively increases, the battery may not meetthe standard.

Although the examples 1 through 11 are made in accordance with theembodiment of FIG. 5, it will be appreciated by those skilled in the artthat the identical effect can be obtained even when the examples aremade in accordance with other embodiments.

The battery modules according to the foregoing embodiments can be usedas the power source for driving motors, such as those for hybridelectric vehicles, electric vehicles, electric scooters, electricbicycles, wireless vacuum cleaners, or the like.

Although exemplary embodiments of the present invention have been shownand described, it will be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

For example, the structures of the projections are not limited to theabove-described embodiments. That is, the projections may be formed in,for example, a rectangular cylinder shape.

1. A rechargeable battery comprising: an electrode assembly having apositive electrode and negative electrode and a separator interposedbetween the positive and negative electrodes; a case for receiving theelectrode assembly; and a plurality of projections formed on an outersurface of the case.
 2. The rechargeable battery of claim 1, wherein theprojections are random in terms of a size and shape.
 3. The rechargeablebattery of claim 1, wherein the projections are random in terms of anarrangement thereof.
 4. The rechargeable battery of claim 1, whereineach of the projections has a circular section.
 5. The rechargeablebattery of claim 1, wherein each of the projections has a rectangularsection.
 6. The rechargeable battery of claim 1, wherein the projectionsare uniformly arranged in a predetermined pattern.
 7. The rechargeablebattery of claim 1, wherein the projections are distributed throughoutthe outer surface.
 8. The rechargeable battery of claim 1, wherein thecase is prismatic.
 9. The rechargeable battery of claim 1, wherein thecase is cylindrical.
 10. The rechargeable battery of claim 1, whereinthe projections are integrally formed with the case.
 11. Therechargeable battery of claim 1, wherein, when it is assumed that anarea of a case having an even outer surface is 100, the projections areformed such that a relative area of the outer surface of the case isabout 150 or more.
 12. The rechargeable battery of claim 11, wherein theprojections are formed such that a relative area of the outer surface ofthe case is in the range from 150 to
 1000. 13. The rechargeable batteryof claim 11, wherein the projections are formed such that a relativearea of the outer surface of the case is in the range from 175 to 1000.14. A battery module comprising: a housing having an inlet forintroducing cooling air and an outlet for exhausting the introducedcooling air; and a plurality of unit batteries disposed in the housing,each unit battery having a case whose outer surface is provided with aplurality of projections.
 15. The battery module of claim 14, whereinthe projections are distributed throughout the outer surface of thecase.
 16. The battery module of claim 14, wherein the projections arerandom in a size, shape and arrangement.
 17. The battery module of claim14, wherein the projections are uniformly arranged in a predeterminedpattern.
 18. The battery module of claim 14, further comprising barriersinterposed between the unit batteries such that gaps are defined betweenthe barrier and the unit battery by the projections.
 19. The batterymodule of claim 14, wherein, when it is assumed that an area of a casehaving an even outer surface is 100, the projections are formed suchthat a relative area of the outer surface of the case is about 150 ormore.
 20. The battery module of claim 19, wherein the projections areformed such that a relative area of the outer surface of the case is inthe range from 150 to
 1000. 21. The battery module of claim 19, whereinthe projections are formed such that a relative area of the outersurface of the case is in the range from 175 to 1000.